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SubjectRe: tools lib traceevent: Report better error message on bad function args
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Hi Steven,

On Mon, 18 Nov 2013 19:11:31 -0500, Steven Rostedt wrote:
> When Jiri Olsa was writing a function callback for
> scsi_trace_parse_cdb(), he thought that the traceevent library had a
> bug in it because he was getting this error:
>
> Error: expected ')' but read ','
> Error: expected ')' but read ','
> Error: expected ')' but read ','
> Error: expected ')' but read ','
>
> But in truth, he didn't have the write number of arguments for the
> function callback, and the error was the library detecting the
> discrepancy. A better error message would have prevented the confusion:
>
> Error: function 'scsi_trace_parse_cdb()' only expects 2 arguments but event scsi_dispatch_cmd_timeout has more
> Error: function 'scsi_trace_parse_cdb()' only expects 2 arguments but event scsi_dispatch_cmd_start has more
> Error: function 'scsi_trace_parse_cdb()' only expects 2 arguments but event scsi_dispatch_cmd_error has more
> Error: function 'scsi_trace_parse_cdb()' only expects 2 arguments but event scsi_dispatch_cmd_done has more
>
> Or
>
> Error: function 'scsi_trace_parse_cdb()' expects 4 arguments but event scsi_dispatch_cmd_timeout only uses 3
> Error: function 'scsi_trace_parse_cdb()' expects 4 arguments but event scsi_dispatch_cmd_start only uses 3
> Error: function 'scsi_trace_parse_cdb()' expects 4 arguments but event scsi_dispatch_cmd_error only uses 3
> Error: function 'scsi_trace_parse_cdb()' expects 4 arguments but event scsi_dispatch_cmd_done only uses 3
>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
>
> diff --git a/tools/lib/traceevent/event-parse.c b/tools/lib/traceevent/event-parse.c
> index 0362d57..f7aab3d 100644
> --- a/tools/lib/traceevent/event-parse.c
> +++ b/tools/lib/traceevent/event-parse.c
> @@ -2691,7 +2691,6 @@ process_func_handler(struct event_format *event, struct pevent_function_handler
> struct print_arg *farg;
> enum event_type type;
> char *token;
> - const char *test;
> int i;
>
> arg->type = PRINT_FUNC;
> @@ -2708,15 +2707,19 @@ process_func_handler(struct event_format *event, struct pevent_function_handler
> }
>
> type = process_arg(event, farg, &token);
> - if (i < (func->nr_args - 1))
> - test = ",";
> - else
> - test = ")";
> -
> - if (test_type_token(type, token, EVENT_DELIM, test)) {
> - free_arg(farg);
> - free_token(token);
> - return EVENT_ERROR;
> + if (i < (func->nr_args - 1)) {
> + if (type != EVENT_DELIM || strcmp(token, ",") != 0) {
> + warning("Error: function '%s()' expects %d arguments but event %s only uses %d",
> + func->name, func->nr_args,
> + event->name, i + 1);
> + return EVENT_ERROR;
> + }
> + } else {
> + if (type != EVENT_DELIM || strcmp(token, ")") != 0) {
> + warning("Error: function '%s()' only expects %d arguments but event %s has more",
> + func->name, func->nr_args, event->name);
> + return EVENT_ERROR;

It seems that you missed to free farg and token in error paths.

Thanks,
Namhyung


> + }
> }
>
> *next_arg = farg;


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